I found that this error could be consistently reproduced on bionic. The problem occurs if /var/lib/mysql already exists before installing the packages.
Steps to reproduce, from a bare install of Ubuntu server: 1) sudo mkdir /var/lib/mysql 2) sudo apt install mysql-server The annoying thing is that even if you then run "sudo chown mysql:mysql /var/lib/mysql" (after the first attempt created the user and group), and re-run the install, it still doesn't work even though it creates some files in /var/lib/mysql . The use case for why you would want to pre-create /var/lib/mysql is when you want it on a separate filesystem. The required steps to achieve this are as follows; if necessary, ensure you purge the package and delete the contents of /var/lib/mysql (except lost+found) first. sudo umount /var/lib/mysql sudo rmdir /var/lib/mysql sudo apt install mysql-server sudo service mysql stop sudo mv /var/lib/mysql /var/lib/mysql.tmp sudo install -m 0 -d /var/lib/mysql # Create mount point with no permissions sudo mount /var/lib/mysql # Assumes filesystem is created and listed in /etc/fstab sudo sh -c 'mv /var/lib/mysql.tmp/* /var/lib/mysql' sudo rmdir /var/lib/mysql.tmp/ sudo service mysql start ** Changed in: mysql-5.7 (Ubuntu) Status: Expired => Confirmed -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1785693 Title: package mysql-server-5.7 5.7.23-0ubuntu0.18.04.1 failed to install/upgrade: installed mysql-server-5.7 package post-installation script subprocess returned error exit status 1 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/mysql-5.7/+bug/1785693/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs